1. Field of the Invention
The present invention relates to an image processing apparatus for converting color image data into those corresponding to an image outputting apparatus.
2. Description of Related Art
Recently, color printers became popular with the debut of low-price ink jet printers, and the like. Due to rapidly widespread use of the Internet, it became possible to easily print a Web image such as a home page containing characters and photos and appearing on a monitor display, with a color printer.
When a Web image such as a home page on a monitor display is to be printed, it is desirable to compensate for insufficient functions of the browser used to obtain the image. Therefore, a printer driver software for the Internet additionally including functions such as automatic magnification, automatic page ejection, and multiple column setting has been developed. Such a driver controls a printer so as to faithfully print an image displayed on the monitor.
A Web image in a home page or the like on the Internet sometimes includes characters having high brightness such as white or yellow which can be very easily identified in a background color on a monitor, particularly in the case where the home page is in its own color setting. On the monitor display, characters of high brightness such as white or yellow in the background of low brightness are very clearly viewed.
In the case where, for example, the home page is in its own color setting, if the Web image is directly printed out by a color printer or the like so as to be faithfully reproduced, only the character portion is printed out and the background color is not printed out onto a paper sheet. In such a case, the screen image on the monitor display can be easily recognized with a large difference in brightness from the background. In contrast, on a printed paper sheet, it is very difficult to recognize characters and small graphics with no difference in brightness from the background, because they have a small brightness difference. In the worst case, such characters and small graphics cannot be substantially identified.
Many techniques for converting colors have been hitherto proposed.
In an image processing apparatus disclosed in Japanese Patent Publication (Kokai) No. HEI9-219797, a plane region containing colors before conversion and configured by hue and chroma is adjusted in a range which does not overlap a region including specified colors. The region is subjected to color conversion into specified colors based on a conversion color code.
In an image processing apparatus disclosed in Japanese Patent Publication (Kokai) No. HEI9-331464, color information which is selected by the operator from registered color information is converted by using a hue conversion coefficient, and then stored in a hue data memory as a registered color.
However, these methods are ineffective for an achromatic color such as white. As for chromatic colors, color information in other image regions such as graphics or photographic regions may be disadvantageously changed. Accordingly, it is impossible to sufficiently use such color management functions.
It is an object of the invention to provide a color image processing apparatus in which the ease of reading of bright characters printed onto a paper sheet is improved.
According to the present invention, an image processing apparatus comprises brightness extracting means for extracting information relating to brightness from color image data; image attribute judging means for judging a light-color image portion in a color image; and a lightness change section which changes brightness of the light-color image portion. The image attribute judging means comprises separating means for separating foreground data and background data from the color image data; and a comparing section which, when a difference in brightness between the foreground and the background separated by said separating means is smaller than a predetermined value, judges the foreground data as data of a light-color image portion.